FontBook Issues

I'm running an imac on OSX 10.9.5

Have been having problems with very long delays on start up / opening applications etc.

Finally had a lightbulb moment when i realised Photoshop was loading a lot of fonts i'd never heard of before so...

Had a major purge of my font files and stripped them right back to essentials.

Ok - so far so good - my imac is responding a lot more healthily now, however....

FontBook is not looking right at all...

Firstly there are fonts in my library_fonts and system_library_fonts folders, (my user-library-fonts file is currently empty) that are not showing up in the 'all fonts' listing in FontBook

Secondly if i drag fonts from the 'all fonts' listing to a collection it only drags some of the fonts - most are not copied across

I don't want to start adding fonts to my user_library_fonts file until I'm satisfied FontBook is behaving and not causing problems.

My next step was to try uninstalling fontbook entirely from my imac and then re-installing it.

I can't see an option to do that from the fontbook menus but presumably I need to delete any associated files/databases that fontbook has created.

Any advise on how I should proceed - or any alternative and less drastic procedures would be appreciated.